1. Technical Field of the Invention
The present invention relates to liquid crystal devices for displaying images such as letters and numerals by modulating light using liquid crystal. The present invention also relates to electronic apparatuses using the liquid crystal devices.
2 . Description of the Related Art
In recent years, reflective liquid crystal devices have been frequently used for display units of electronic apparatuses such as mobile apparatuses. Since a light source such as a backlight is not provided in the reflective liquid crystal device, they have enjoyed the advantage of reduced electric power consumption. However, since external light is used as the light source, there has been a problem in that the display cannot be viewed in dark places. In view of the above situation, a transflective liquid crystal device has been provided in which the display can be viewed in bright places using external light similar to the reflective liquid crystal device and can also be viewed in dark places using light emitted from a light source such as a backlight.
FIG. 12 is a view showing a schematic structure of a conventional transflective liquid crystal device 100. The transflective liquid crystal device 100 shown in the figure is an active matrix liquid crystal device using TFD (Thin Film Diode) elements as a switching element.
In this transflective liquid crystal device 100, between an upper substrate 101 and a lower substrate 102 each having transparency and insulating properties, liquid crystal 103 is enclosed by a frame-shaped sealing material (not shown in the figure), and accordingly, a liquid crystal cell 110 is formed.
On the inside surface of the upper substrate 101, a plurality of rectangular pixel electrodes having transparency formed of ITO or the like is provided and is connected to metal wires (not shown in the figure) via the TFD elements. In addition, at the outside surface side of the substrate 101, a polarizer 121 and a retardation film 122 are provided in this order from an observer side.
In addition, at the inside surface side of the lower substrate 102, a transflector 131, a black matrix or a black mask for absorbing light, that is, shading films 132, and counter electrodes 135 are sequentially provided in this order, and at the outside surface side of the lower substrate, a retardation film 142, a polarizer 141, and a backlight 150 are provided. Since other elements (such as color layers, an alignment film, and a protective layer) constituting the transflective liquid crystal device 100 are not specifically necessary for describing display operation of the transflective liquid crystal device, they are not shown in the figures, and the descriptions thereof are omitted.
In the transflective liquid crystal device 100 having the structure described above, when external light from the observer side enters the device while the device is in the white display state, in an electrode existing area at which the pixel electrode 111 is provided on the upper substrate 101, as shown by a light path A, the incident light passes through the polarizer 121, the retardation film 122, the upper substrate 101, the pixel electrode 111, the liquid crystal layer 103, and the counter electrode 135 in this order and reaches the transflector 131, and the light reflected at the transflector 131 retraces the path through which it passed and is emitted from the polarizer 121 to the observer side.
In contrast, in a non-electrode existing area at which the pixel electrode 111 is not provided on the upper substrate 101, incident light is absorbed by the shading film 132 provided at the lower substrate 102 side as shown by a light path B.
In addition, when light is emitted from the backlight 150, in the electrode existing area, as shown by a light path C, the emitted light from the backlight 150 passes through the polarizer 141, the retardation film 142, the lower substrate 102, the transflector 131, the counter electrode 135, the liquid crystal layer 103, the pixel electrode 111, the upper substrate 101, the retardation film 122, and the polarizer 121 in this order and is emitted to the observer side.
In contrast, in the non-electrode existing area, emitted light is absorbed by the shading film 132 provided at the lower substrate 102 side as shown by a light path D.
As described above, in the conventional transflective liquid crystal device 100, a display is created by reflecting the light entered into the liquid crystal layer 103 from the observer side at the transflector 131 when the environment is bright, and on the other hand, when the environment is dark, a transmissive display is created by transmitting the light emitted from the backlight 150 through the transflector 131.
Although the conventional transflective liquid crystal device has an advantage in that a reflective display and a transmissive display can both be created depending on the environment in which it is used, since the light loss rate of the conventional transflective liquid crystal device is high, there has been a problem in that the display image is dark. In addition, as well as the transflective liquid crystal device, it has also been demanded to increase the brightness of the display image of the reflective liquid crystal device and the transmissive liquid crystal device.
In view of the situations described above, the present invention was made, and an object of the present invention is to provide a liquid crystal device having a high aperture ratio and superior display properties and to provide an electronic apparatus provided with the liquid crystal device described above.